When an image is captured by an imaging device, for example a camera, the image does not represent a single instant of time but it represents the scene over a period of time. So due to a relative movement between the object and the camera, the image will be blurred. Motion blur often happens due to unsteady hand movement so that the image will be smeared along the direction of relative motion.
Due to a longer exposure time, e.g. in low light conditions, the corresponding picture can be blurred due to handshaking or other motion of the imaging device during the captured time. To properly deblur the taken image is important to create a point spread function with correct values.
The estimation of the point spread function thus can be complex or may lead to insufficient results, which do not lead to a good deblurring result.